Electronic signal generator



Patented May 31, 1949 UNITED STATES TENT OFFICE ELECTRONIC SIGNALGENERATOR Donald E. Norgaard, Scotia, N. Y., assignor to GeneralElectric Company, a corporation of New York 12 Claims. 1

This application is a division of my copending application, Serial No.446,231, filed June 8, 1942, entitled Cathode ray apparatus, andassigned to the same assignee as the instant application.

My present invention relates to pulse systems, and particularly toelectric impulse generating circuits. The invention is especiallyapplicable to radio echo finding equipment and radio communicationequipment. As described in the above copending application, electricvoltage pulses of the described character may be used in a variety ofways, such as to control cathode ray discharge devices and the like.

It is a general object of my invention to provide a new and improvedelectric circuit for the generation of electric impulses of shortduration.

It is a further object of my invention to provide I a new and improvedtransient voltage response circuit for generating electric voltagepulses having a duration of the order of less than a microsecond.

In accordance with my invention, a substantially rectangular voltagewave is impressed upon a circuit of such character that the leading edgeof each rectangular half wave initiates a transient or damped highfrequency oscillation which is thus superposed upon the square wave. Thethus distorted square wave is then differentiated to exaggerate thedifference in amplitude between the first and second positive voltageswings of the high frequency oscillations occurring during each halfcycle of the square wave voltage. The resulting wave is then used tocontrol a clipper tube which is so biased that it does not conductunless its control Voltage is raised above a threshold value less thanthe first positive high frequency voltage peak, but greater than theremainder of the distorted square wave. In this manner the clipper tubeis triggered upon each positive half cycle of square wave voltage andfor the duration of less than a half cycle of the superposed highfrequency oscillation.

My invention itself will be more fully understood and its objects andadvantages further appreciated by referring now to the followingdetailed specification taken in conjunction with the accompanyingdrawing, in which Fig. 1 is a schematic circuit diagram of a pulsegenerating circuit embodying my invention; and Figs. 2, 3 and 4 aregraphical representations of certain of the vialtage characteristics ofthe circuit shown at At Fig. 1, I have shown at I a source ofoscillations having a frequency equal to the desired repetition rate ofthe pulses to be generated,

The character of the source I is not an essential feature of the presentinvention, but preferably the source I comprises a crystal or electrondischarge oscillator having an output voltage of substantially sine waveshape. Likewise, the frequency of the source I is immaterial to theoperation of my invention. By way of example, however, reference may behad to my aforementioned copending application, wherein is described acomplete cathode ray apparatus utilizing my present invention with thesine wave source I having a frequency of approximately 82 kilocycles Persecond.

The sine wave output from the source I is connected to the input of anamplifier and limiter 2. The amplifier and limiter 2 may be of anysuitable type designed to supply at its output circuit a square wavederived from the sine wave input from the source I. At Fig. 4 I haveshown a curve 3 representing the sine wave applied to the input of theamplifier and limiter 2. As a result of its amplitude limiting action,the output of the limiter 2 has the form of the approximately squarewave 4 of Fig. 4.

The square wave voltage output from the limiter 2 is applied to the gridor input control electrode 5 of an electron discharge amplifying device6. The amplifier 6 includes a cathode I, a screen grid 8, a suppressorgrid 9 and an anode Ill. The cathode I is grounded through a resistor Iaand bypass condenser lb. The amplifier anode I0 is connected through aninductance I l and resistances I2 and I3 to a suitable source ofpositive I anode potential, such as a battery I4. The battery I 4 isgrounded at I 4a and the battery and resistor I3 are by-passed to groundby a condenser I5. The screen grid 8 of the amplifier 6 is supplied witha suitable positive potential from an intermediate point I6 on thebattery I4. The suppressor grid 9 is connected directly to ground.

In operation the square wave applied to the amplifier control grid 5produces square wave pulses of current in the amplifier anode circuitincluding the inductance II, resistance I2, and by-pass condenser I5.This anode circuit is shunted by a certain amount of inherent stray anddistributed capacitance, represented on the drawing by a condenser I'Ishown in dotted lines. It will be understood that each change in currentin the inductance II initiates a transient voltage oscillation in theresonant anode circuit II, I2, I 5, II. This damped voltage oscillationhas a frequency determined by the constants of the resonant anodecircuit itself, and this frequency is much higher than the frequency ofthe square I of each high frequency oscillatory transient is ofconsiderably greater amplitude than the later cycles, since theoscillatory transient is rapidly damped throughout the period or eachhalf cycleof the square wave oscillations,

The square wave 4, with its superposed oscillatory transient I3, issupplied to a .diflierentiating circuit comprising a condenser 21. anda; resistance 22 connected in series circuit relation with a suit ablesource of negative biasing potential, such as a battery 23, across theresonant anode circuit of the amplifier 6. The voltage across theresistance 22 and battery 23 in series is applied between the cathode 24and control electrode or grid 25 of an electron discharge. device orclipper tube 26. The battery 23 is grounded at Ma and serves to biasthe. control electrode 25 negatively, so that the discharge device 23will not conduct except when positive potential above a certainpredetermined threshold value is supplied through the coupling condenser2|. The discharge device 26 includes also a screen electrode 27connected to the point l6 on the battery I4, a suppressor electrode 28connected. directly-to. ground at Ma and an anode 29 connected through aload resistor 30. to the positive terminal of the battery M. The anodevoltage of the discharge device 23 is supplied through a couplingcondenser 31 to any suitable utilization circuit which may, for example,comprise the deflection electrodes of a cathode ray discharge. device.

By reason of the operation of the diiferentiating circuit including thecondenser 2 I, the square voltage. wave 4' is not reproduced as a squarewave across the resistor 22', but rather appears thereon in the form ofthe wave represented by the dotted line 32 of Fig. 2. That is, when thecurrent is a minimum in the device 6, its anode It is at high positivepotential and the condenser 2! assumes a certain charge. During apositive pulse on the grid ofthe device 6, current increases in theanode I'll thereby causing the condenser 2! to discharge to a certainextent through the resistor 2.2, as represented by the portion 32a ofthe curve 32 of Fig. 2. During the negative portion of the square wave,the current drops in the device 6 and its anode potential rises. Thecondenser 2| then commences to charge and current flows in,

the. resistor 22 in accordance with the portion 32b of the curve 32 ofFig. 2. The cycle repeats continuously in this manner. It will be seenthat the portions 32a and 32b of the curve 32 are quite steep. It willbe understood, of course, that the transient oscillations 19 of Fig. 3are superposed also upon the curve 32, as represented at Fig. 3 by thecurve I 3a. However, because of the steepness of the charge anddischarge portions of the curve 32 of Fig. 2, the difference in the peakamplitudes of the first and second positive voltage swings of eachtransient oscillation is greatly exagg-erated in comparison to theamplitude diiierence apparent on the square wave base of Fig. 3.

The resultant voltage wave of Fig. 2 appears across the resistor 22 andis applied to the grid or the discharge device 29. The discharge device29, is biased negatively by the battery 23 to such an extent that apositive voltage greater in amplitude than a threshold voltage 33 ofFig. 2 must appear upon the grid 25 before the discharge device 23conducts. Accordingly, it is evident that no part of the voltage wave ofFig. 2 has any eiTect upon the discharge device 2t except the firstpositive high frequency oscillatory voltage swing 2110, at the leadingedge of each positive half cycle of the low frequency oscillations. Itis only this first transient voltage swing which ex- .ceeds thethreshold voltage 33 necessary to overcome the cutoff bias of thedischarge device 26. Accordingly, in the-anode circuit of the dischargedevice :26, pulses of current flow only once per cycle of the squarewave 'oscillations and for only the period of a portion pf the shorttransient positive iql as svt tile I 13; i151; be understood that thesecurrent pulses may be qf high intensity and are of very short duration.For example, when the source I has a frequency of 82 kilocycles persecond, the duration or .ene positive half cycle of the square wave l8of Fig. 3 is approximately 6 microseconds, so. that the duration of apulse. discharge resulting from the transient positivevoltage swing .29a. of Fig. 2 will bev of even much shorter duration.

While'I have described only one preferred ems 1. In-combination, asource of sine Wave electroe I motive force, means to convert, said sinewave. electromotive torce to unidirectional electromotive forcevaryingcyclical'ly and abruptlybetween different values, means-to.superpose upon consecutive force an oscillatory transient of rapidlyd8.- creas ng intensity during the half cycle to. produce a combinedwave in which a sharp intense pulse.

or maximum amplitude is produced at the begin-, nin of each of alternatehalf cycles, a load circuit,

and means to select said sharp intense pulses. and

to supply them to. said load circuit.

2. In combination, a source of square wave voltage, means to convertsaid square. wave volt-v a e to a voltage of wave form having maximumintensity in one polarity at the beginning of each alternate halt-cycle,means to superpose upon consecutive half cycles of said voltage anoscillatory transient of rapidly decreasing intensity during therespective half cycle to produce a combined wave, a load circuit, andmeans to supply to said load circuit a single pulse in response to theoscillatory transients superposed upon alternate half-mycles of saidvoltage in said combined wave.

.3, In combination, an electron discharge device having an anode, acathode, and a control electrode, a source of square waves connectedbetween said control electrode and cathode, a source ofoperatingpotential, an inductance and a resistance. connected between said anodeand cathode whereby said square waves are reproduced between said anodeand cathode, means providing capacity between said anode and cathoderesonating with said inductance at a frequency much higher than thefrequency of said square wave, whereby an oscillatory transient issuperposed upon each half cycle of said square wave in said anodecircuit to produce a combiped wave, a resistance and a condenser contive. half cycles of said unidirectional electromo,-

nected between said anode and cathode, a load circuit, and means to passcurrent to said load circuit in response only to variations in voltageon said last resistance due to said combined wave exceeding thevariations produced thereon by said second square waves alone.

4. A pulse generating circuit comprising a source of electricoscillations of substantially rectangular Wave form and of relativelylow frequency, means for superposing upon consecutive half cycles ofsaid rectangular oscillations transient oscillations of appreciablyhigher frequency and rapidly decreasing intensity to produce a combinedwave, and means responsive only to said high frequency oscillations atthe beginning of each of alternate half cycles said combined wave toinitiate discrete voltage pulses of short duration.

5. A pulse generating circuit comprising a source of electricoscillations of substantially rectangular wave form and predeterminedfrequency, means for superposing upon each half cycle of saidrectangular wave high frequency oscillations of rapidly diminishingintensity to produce a combined wave, and means responsive only to themaximum half cycle intensity of one polarity in said high frequencyoscillations in said combined wave for establishing a discrete voltagepulse duration once per cycle of said rectangular wave.

6. A pulse generating circuit comprising a source of electricoscillations of substantially rectangular wave form and predeterminedfrequency, means for superposing upon half cycles of said rectangularwave damped oscillations of appreciably higher frequency to provide acombined wave having half cycles of oscillatory and diminishingintensity, means for differentiating said combined wave to exaggeratethe decrease in intensity of half cycles of said combined wave, andmeans responsive only to the initial oscillatory intensity of saiddifferentiated wave for establishing discrete voltage pulses of shortduration.

7. A pulse generating circuit comprising a source of electricoscillations of substantially rectangular wave form and predeterminedfrequency, means for superposing upon each half cycle of saidrectangular waves a damped high frequency transient oscillation ofrapidly diminishing intensity, an electron discharge device including ananode, a cathode, and a control electrode, means for impressing thecombined oscillations upon said control electrode, and means forrendering said discharge device substantially non-responsive tooscillations below a predetermined threshold intensity less than themaximum intensity of said combined oscillations.

8. A pulse generating circuit comprising an electron discharge devicehaving an anode, a cathode, and a control electrode, means for supplyingto said control electrode electric oscillations of substantiallyrectangular wave form and predetermined frequency, an anode circuit forsaid discharge device including a resonant circuit tuned to a frequencyappreciably higher than said predetermined frequency, said resonantcircuit superposin upon each rectangular half wave in the output of saiddischarge device a damped high frequency oscillation, and meansresponsive only to the initial maximum intensity of one polarity inalternate half cycles of the combined oscillations for establishingdiscrete electric pulses having a duration of the order of a half cycleof said high frequency oscillations.

9. A pulse generating circuit comprising an electron discharge devicehaving an anode, a cathode and a control electrode, means for supplyingto said control electrode electric oscillations of substantiallyrectangular wave form and predetermined frequency, an anode circuit forsaid discharge device including energy storing means for superposingupon each rectangular half wave in said anode circuit transient electricoscillations of high frequency and rapidly diminishing amplitude, meansfor differentiating the combined oscillations in said anode circuit toexaggerate the amplitude difference between first and second cycles ofsaid high frequency oscillations, a second electron discharge device,means for supplying said differentiated oscillations to said secondelectron discharge device, and means for rendering said second electrondischarge device substantially non-responsive to oscillations havingless than a predetermined threshold amplitude, said differentiatedoscillations exceeding said threshold amplitude only at the said firstcycle of each of said transient oscillations occurring in alternatehalf-cycles of said first-mentioned oscillations.

10. A pulse generating circuit comprising an electron discharge devicehaving an anode, a cathode and a control electrode, means for supplyingto said control electrode electric oscillations of substantiallyrectangular wave form and predetermined frequency, an anode circuit forsaid discharge device including energy storing means, said energystoring means superposing upon each half cycle of said rectangularoscillations damped high frequency oscillations, a second electrondischarge device having an anode, a cathode and a control electrode,means for normally maintaining said second discharge devicenon-conductive, and means for supplying to the control electrode of saidsecond discharge device the combined oscillations in said anode circuit,thereby to trigger said second discharge device once per cycle of saidrectangular oscillations and for the duration of one half cycle of saidhigh frequency oscillations.

11. A pulse generating system comprising, in combination, means toproduce a periodic pulse Wave having maximum intensity in one polaritywith respect to the alternating current axis of said wave near thebeginning of each pulse of said polarity, means to superpose upon eachsaid pulse a relatively high frequency, damped oscillatory transientalso having maximum intensity of said polarity near said beginning,thereby to form a combined wave having a short intense peak near thebeginning of each said pulse, a load circuit, and means to supply tosaid load circuit a single short pulse in response to each of said peaksof said combined wave.

12. A pulse generating system comprising, in combination, means toproduce a periodic pulse wave having maximum intensity in one polaritywith respect to the alternating current axis of said wave near thebeginning of each pulse of said polarity, means to superpose upon eachsaid pulse a relatively high frequency, damped oscillatory transientalso having maximum intensity of said polarity near said beginning,thereby to form a combined wave having a short intense peak near thebeginning of each said pulse, means to select only peak portions of saidcombined wave exceeding said maximum intensity, and means to supply saidpeak portions to a utilization circuit.

DONALD E. NORGAARD.

(References on following page) REFERENC, S CITED Number 2 The [followingreferences are of record in the file of thls patent. UNITED STATESPATENTS 5 2,420,013,

Number Name Date 2,103,090 Plebanski Dec. 21, 193'? N 2,153,202 NicholsApr. 4, 1939 32% 2,181,309 Andrieu Nov. 28, 1939 2,237,661 Ernst Apr. 8,1941 1 Hame Date Barber ..V.. Oct. 14, 19.41., Tubbs v Dec. 16, 1941Wolff June 11, 1946 Rajcham V May 6, l9?! FOREIGN PATENTS Country DateSweden, Sept. .23, 1,938

